1. Field of the Invention:
The present invention relates to an improved automatic paper feeding device for a facsimile equipment or the like apparatus and more particularly to an automatic paper feeding apparatus in which optimum paper feeding is assured without any influence of fluctuation in contact pressure between a feeding roller and a reversing roller.
2. Description of the Prior Art:
A hitherto known automatic feeding device of the type including a feeding roller adapted to rotate in the direction of feeding of papers and a reversing roller adapted to rotate in the opposite direction to that of feeding of papers in a line contact relation with respect to the feeding roller so that papers are drawn one by one under cooperation between both the rollers is generally arranged such that a single endless timing belt is extended round pulleys on both the rollers so as to rotate them simultaneously.
To facilitate understanding of the invention it will be helpful that the conventional device of the above mentioned type will be briefly described.
FIG. 1 schematically illustrates a typical conventional automatic paper feeding device for a facsimile equipment or the like by way of a vertical sectional view. Specifically, a paper feeding board (manuscript holding board) 2 is fixedly secured to side walls 2 at a predetermined inclination angle relative to a horizontal plane and a feeding roller 3 is rotatably mounted on a shaft 4 which extends between both the side walls 1. The feeding roller 3 is made of elastomeric material such as neoprene sponge rubber or the like material which has a high frictional coefficient .mu.1 when it is in use in cooperation with a sheet of paper MS such as manuscript or the like. Further, a pair of levers 5 are held pivotally about a shaft 6 so that a reversing roller 7 is rotatably mounted on a shaft 8 at the free end part of said levers 5. The reversing roller 7 is made of another elastomeric material such as polyurethane rubber or the like material which has a frictional coefficient .mu.2 appreciably lower than the first mentioned one .mu.1. It should be noted that papers in the form of a sheet (hereinafter referred to simply as paper) a frictional coefficient .mu.3 when they are brought in contact with one another, said frictional coefficient .mu.3 being lower than the last mentioned one .mu.2 and therefore a correlation is established among them as represented by an inequality (.mu.1&gt;.mu.2&gt;.mu.3). The lowermost end part 5a of the lever 5 is adapted to abut against the foremost end of a screw 10 which extends through a stay 9 fixedly secured to the side walls 1 so that contact pressure between both the rollers 3 and 7 can adjusted by rotating the screw 10. A shaft 11.sub.a of a driving motor 11, the shaft 4 of the feeding roller 3 and the shaft 8 of the reversing roller 7 include pulleys 13, 14 and 15 fixedly mounted thereon respectively and an endless timing belt (driving belt) 16 is extended round each of the pulleys 13, 14 and 15 so that the rollers 3 and 7 are rotated in the same direction as identified with an arrow mark A.
The arrangement as described above makes it possible to draw out papers one by one from the bottom of the layer of sheet papers MS placed on the paper feeding board 2 while the feeding roller 3 cooperates with the reversing roller 7.
It is found with respect to the illustrated conventional device that due to tension given by the endless timing belt 16 the levers 5 are caused to turn in the counterclockwise direction to approach closer to the roller 3, resulting in increased contact pressure between both the rollers 3 and 7, said increased contact pressure being varied as the endless timing belt 16 is circulatively operated. When the contact pressure increases in excess of a properly determined level, there is a fear of causing a trouble that the paper MS is inhibited from entering in the contact area between the feeding roller 3 and the reversing roller 7 or it is fed thereinto in the wrong manner. In the extreme case the paper may damaged or injured.
Further it is found with respect to the conventional automatic paper feeding device that as it continues to be operated contact pressure between the rollers is gradually reduced due to an occurrence of wearing of the rollers and moreover proper contact pressure fails to be maintained because of decrease in diameter of the rollers when environmental conditions change, particularly when it becomes cool. When contact force decreases, the rollers have a reduced capability of separating the papers one from another and therefore it happens that the plural number of papers are fed simultaneously.